Rotary bit for drilling coal and rock



Feb. 1949 R W. WINN 2,461,305

ROTARY BIT FOR DRILLING COAL AND ROCK Filed Sept. 14, 1944 Patentecl Feb. 8, 1949 UNITED s'rArss t 'ENT OFFICE homer -arr FOR" DRILLING coAL I AND ROCK William Winn,,Monkseaton, England, assignor to Victor Products (Wal company lsend) Limited, a British Application September 14, 1944 Serial No.554, 03'0 In Great Britain SeptemberZZ, 1943 3 Claims. (Cl. ass-sci) This invention relates to rotary bits such as are used for drilling shot holes in coal and stone. It is the object of the invention to enable larger diameter holes to be made than those normally possible with manually operated hand-held drills commonly in use, or alternatively to enable smaller sized holes within the capacity of such drills to be drilled more quickly and with less risk of breakage of the drilling bit. The invention comprises a novel design Offlri'l'ling bit which varies from those normally in use.

Existingpractice in the main covers the use of three types .of bits, as follows:

1. The eccentric bit arranged with cutting faces of unequal length which causes the drilling bit to adopt a wobbling movement and tends to avoid the making of a core. This bit commonly called a wobble bit, is intended to be used in average material where the natural strength of the core of the material being drilled is not such as to cause the tips of the bit to be smashed by their unequal cutting faces.

2. A bit with equal cutting faces known as the concentric bit intended to be used where the core of the material being drilled is such as will prevent the bit wobbling as indicated in the pre-.

ceding paragraph, i.e. certain types of exceptionally hard coal and more broadly, stone of varying descriptions.

3. A bit with a v-sloped gap known as the V bit which gives the same cutting effect as a concentric bit, With the exception that the shape of the V cuts away the core. This bit is used with exceptionally woody coal where the fibrous nature of the core prevents it breaking, although the material is not sufficiently hard in itself to damage the tips.

Apart from the above types accepted as standard we have designed a bit to deal with exceptionally friable coal, where there is no tendency for a core to form and where the effective gap of the bit can therefore be very wide, and advantage can be taken of this to have widely sloping cutting edges. This form of bit has been called the S type, and is described in British patent specification No. 500,147.

In actual operation the difference between the wobble bit and a concentric bit is that the wobble bit is a much faster cutting tool while, in the material with which it is capable of being used, the S type bit is again very much faster than the concentric bit.

This range of known bits leaves a gap where a bit is required to deal with hard coal, not sufficiently hard to necessitate a concentric bit with its comparatively slow rate of drilling, but sufiiciently hard toprovid'e such a core as would slow down the drilling with a wobble bit and at the same time would tend to injure the cutting faces of the bit. 7

It has been found possible to retain the general design of existing'bits with 'amodificationwhich in effectserves to break down the core when drilling such material, and it is the peculiar features of this modification which form thesubject of the present invention.

In the new form of bit, chewing may-be of-any usual construction and shape, such that=theinside edge provides a parallel face to :the core. The other wing of the bit may have any usual construction and shape of forward cutting edge, but its inner edge is cut back so that it takes up an angle to the core. It might be expected that such a bit would fail to break the core and so would be held so rigidly that any cutting edge of the wobble form or a similar form would be injured.

We have found however that such a bit retains its cutting action without injury to the cutting edges and at the same time breaks the core at such a speed that drilling time is considerably re duced and in fact approaches that of the S type bit when used in hard coal.

The invention is illustrated in the accompanying drawings in which:

Figure 1 is a side elevation of one form of the bit;

Figure 2 is an end elevation; and

Figure 3 is a plan view.

The bit shown has a shank It with two wings or blades 82 and M, both provided with hard metal cutting faces is and 58 respectively. The wing i2 is straight in form with its cutting face like that of the straight wing of a concentric or wobble bit, but the wing M has an inclined inner face and its end cutting face in the example shown is of the wobble type having its tip or apex 22 substantially further from the axis of the bit than is the tip or apex 20 of the wing I2. The effect is that of a wobble bit but with an inclined inner cutting face on one wing which breaks away the core as fast as it forms. The end cutting face l8 of the wing I4 is not necessarily shaped as in a wobble bit, with its apex 22 substantially further from the axis than is the apex 28 of the cutting face It. The apex 22 might be more nearly equidistant or actually equidistant from the axis with the apex 20' of cutting face It, but the wobble form is generally preferable;

If both wings of the bit were made of the in- 3 ciined type so as to provide a V type bit as normally used for woody coal, then all the advantages above mentioned would be lost, so that it is essential for the purposes of this invention that the wings of the bit should be dissimilar, one being substantiallystraight when seen from the front, while the other has an inclined inner face.

A bit of the type described can of course be used as a pilot bit in association with a reamer.

bit, or can be used as a single bit of any diameter.

I claim:

1. A rotary drilling bit having two wings each with a cutting face whose end is of angular form with a projecting apex spaced from the axis of the bit, one of said wings having its inner edge parallel to the axis of the bit and the other wing having its inner edge throughout the entire extent of the wing inclined from its base outwardly from said axis toward its outer end, and also having the apex of its angular end further from the axis of the bit than is the apex of the other said wing.

2. A rotary drilling bit of the wobble type having two wings each including a hard metal cutting face inset into it, each such cutting face terminating in an angular end spaced from the axis of the bit, the apex of the angular end on one such wing being further from the axis of the bit than is the apex of the angular end of the other such wing, while the inner edge of the wing having its apex nearer to the axis is substantially parallel to said axis, and the inner edge of the other wing whose apex is further from the said axis is inclined from its base outwardly with respect to said axis.

3. A rotary drilling bit of the wobble type having two wings each including a hard metal cutting face inset into it, each such cutting face terminating in an angular end having an apex spaced 5 from the axis of the bit, the apex of the angular end on one such wing being further from the axis of the bit than is the apex of the angular end of the other such Wing, while the inner edge of the wing having its apex nearer to the axis is sub- 1 stantially parallel to said axis, and the inner edge of the other wing whose apex is further from the said axis is inclined from its base outwardly with respect to said axis, the outer edges of both said wings being substantially parallel with and equi- 15 distant from said axis.

WILLIAM WINN.

REFERENCES CITED The following references are of record in the 20 file of this patent:

UNITED STATES PA'I'ENTS 

